A hernia is the protrusion of part of a body part or structure through a defect in the wall of a surrounding structure. Most commonly, a hernia is the protrusion of part of abdominal contents, including bowel, through a tear or weakness in the abdominal wall, or through the inguinal canal into the scrotum.
An abdominal hernia is repaired by suturing or stapling a mesh patch over the site of the tear or weakness. The mesh patch has a rough surface that can irritate the bowel and cause adhesions. It is therefore preferred to install the patch properitoneally (the terms properitoneal and preperitoneal are used as synonyms). The mesh patch is preferably attached to the properitoneal fascia of the abdominal wall and covered by the peritoneum. To attach the mesh patch to the properitoneal fascia, the peritoneum must be dissected from the properitoneal fascia. This is a difficult process which involves the risk of puncturing the peritoneum. Moreover, strands of properitoneal fat interconnecting the peritoneum and the properitoneal fascia make it difficult to see the site of the hernia.
The abdominal wall includes various layers of tissue. The peritoneum (P) is the innermost layer. Overlying the peritoneum are several layers of tissue, including the properitoneal fat layer (FL) and the properitoneal fascia (F). The properitoneal fascia is the layer to which a mesh patch is preferably attached in hernia repair. The properitoneal fat layer separates the peritoneum from the properitoneal fascia. The properitoneal fat layer is relatively weak, which enables the peritoneum to be separated relatively easily from the fascia.
When the peritoneum is separated from the fascia, separation takes place at or in the properitoneal fat layer. The properitoneal fat layer can remain attached to the properitoneal fascia, or can come away with the peritoneum. Alternatively, part of the properitoneal fat layer can remain attached to the peritoneum and part of the fat layer can come away attached to the peritoneum. Because of the uncertainty in the point of separation, the layer which is detached will be called the peritoneum, and the layer from which the peritoneum is detached will sometimes be denoted as the overlying layer. Additional layers of tissue lie between the properitoneal fascia and the skin.
An inguinal hernia occurs when the contents of the abdominal cavity break through the abdominal wall. As described above, a hernia is repaired by attaching a piece of mesh to the abdominal wall. To prevent the mesh from causing trauma to the bowel, either through irritation of the bowel by the rough surface of the mesh, or by adhesion of the bowel to the mesh, it is preferred to attach the mesh to the properitoneal fascia. With the mesh attached to the fascia, the peritoneum covers the mesh and isolates the bowel from the mesh.
Conventional techniques of attaching the mesh patch to the properitoneal fascia, both laparoscopic and normal, involve blunt dissecting the peritoneum away from the properitoneal fascia, working from inside or outside the belly. The apparatus and methods according to the invention enable the peritoneum to be separated from the properitoneal fascia and the mesh patch attached to the fascia without entering the belly.
Although the following description will describe apparatus and methods according to the invention with respect to hernia repair, the inventive apparatus and methods are not restricted to hernia repair. The apparatus and methods can also be used in other procedures in which one layer of tissue is separated from another to form a working space between the layers. These procedures include thoracoscopy in patients with pleural adhesions; pericardioscopy, or the introduction of an endoscope into the pericardial cavity, in patients with pericardial adhesions; retroperitoneal lymph node dissection, in which the peritoneum on the distal aspect of the abdominal cavity is separated from the underlying tissue which includes lymph nodes; and in separating a blood vessel from surrounding connective tissue in the course of, for example, a femoropopliteal arterial bypass graft procedure.
Laparoscopic techniques to perform hernia repair are being used increasingly frequently. In the conventional procedure for carrying out a hernia repair laparoscopically, an endoscope and instruments are introduced into the belly through one or more incisions in the abdominal wall, and advanced through the belly to the site of the hernia. Then, working from inside the belly, a long incision is made in the peritoneum covering the site of the hernia. Part of the peritoneum is dissected from the properitoneal fat layer to provide access to the fat layer. This is conventionally done by blunt dissection, such as by sweeping a rigid probe under the peritoneum. In this procedure, it is difficult to dissect the peritoneum cleanly since patchy layers of properitoneal fat tend to adhere to the peritoneum.
In an alternative known laparoscopic hernia repair procedure, the belly is insufflated. An incision is made in the abdominal wall close to the site of the hernia. The incision is made through the abdominal wall as far as the properitoneal fat layer. The peritoneum is then blunt dissected from the properitoneal fat layer by passing a finger or a rigid probe through the incision and sweeping the finger or rigid probe under the peritoneum. After the peritoneum is dissected from the properitoneal fat layer, the space between the peritoneum and the properitoneal fat layer is insufflated to provide a working space in which to apply the mesh patch to the properitoneal fascia.
During the blunt dissection process, it is easy to puncture through the peritoneum, which is quite thin. Additionally, after initial dissection of the properitoneal space, known surgical procedures require introduction of various instruments in the space to conduct the surgery. These instruments can cause inadvertent puncture of the peritoneum wall after the initial dissection. A puncture destroys the ability of the space between the peritoneum and the fascia to hold insulation gas; pressurized gas can travel through a puncture in the peritoneum to allow the fluid to migrate to the abdominal cavity and degrade the pressure differential maintaining the properitoneal cavity. Also, it is difficult to dissect the peritoneum cleanly since patchy layers of properitoneal fat tend to adhere to the peritoneum. Clearing difficult adhesions can sometimes result in a breach of the peritoneum itself.
U.S. Pat. No. 5,309,896 (of which this application is a C.I.P.), discloses a laparoscopic hernia repair technique that enables a mesh patch to be attached to the properitoneal fascia without breaching the peritoneum. An incision is made through the abdominal wall as far as the properitoneal fat layer. A multi-chambered inflatable retraction device is pushed through the incision into contact with the peritoneum, and is used to separate the peritoneum from the overlying tissue layer. The main end chamber of the inflatable retraction device is then inflated to elongate the inflatable retraction device towards the site of the hernia. As it inflates, the inflatable retraction device gently separates more of the peritoneum from the overlying tissue layer. Once the main chamber of the inflatable retraction device is fully inflated, a second inflatable chamber is inflated. The second inflatable chamber enables the inflatable retraction device to continue to separate the peritoneum from the other tissue layers after the main inflatable chamber has been deflated.
One or more apertures are then cut in the envelope of the main inflatable chamber to provide access to the site of the hernia for instruments passed into the main chamber. With such an arrangement, instruments pass through the main chamber while the main chamber remains between the peritoneum and the overlying layers. In this way, a patch can be attached to the properitoneal fascia without breaching the peritoneum.
Until the present invention, it had not been known how to view a space between tissue layers while (or after) dissecting the layers with a balloon, without removing any portion of the dissecting apparatus including the balloon, but also without image degradation resulting from viewing through balloon wall. Nor, until the present invention, had it been known to design a balloon (suitable for tissue dissection, tissue retraction, and/or instrument anchoring) to have any of a wide range of inflated shape and pressure characteristics. For example, it had not been known to design a tissue dissection balloon to have inflated shape and pressure characteristics tailored for producing a working space (between dissected tissue layers) having a particular size and shape selected from a broad range of sizes and shapes.